Jr., speaking out about his son's addiction problem. The superstar's 20-year-old son was arrested on drug charges over the weekend. And the actor, who has had his well-publicized battle with addiction, says genetics could be to blame. Reena ninan has more. Reporter: He's the superstar who is the driving force behind blockbusters like "The avengers" and "Iron man." This morning, Robert Downey Jr. Is speaking out in support of his son, 20-year-old inowe Downey, released on bail after being arrested Sunday afternoon, on suspicion of possession of cocaine and drug paraphernalia. Downey telling ABC news, there's a genetic component to addiction. And india has likely inherited it. We're all determined to rally behind him and help him become the man he's capable of being. Downey Jr. Has played addicts on the big screen. But off screen, he's been fighting addiction his entire life. Saying for him, addiction started at a very young age. When did you do your first drug? Before I was 8 years old. Addiction is a genetic disorder in the sense that it's a roll of the dice. Do you have that genetic component or not? Just like blue eyes or green eyes. What Robert Downey Jr. Has done in such a beautiful way is to be an example of an addict in recovery. Reporter: But he's also become the success story for overcoming addiction, opening up to Diane sawyer in 2004, two years into his sobriety. We've known each other for so long. But you've seen the whole thing. You know when I was full of crap, back in the cry help days. I could see in your eyes, not quite done yet. You have this feeling of groundedness now and a little humility. It's really liberating. Reporter: Now, he's hoping to see his son through this dark time he knows so well. Telling us, we're grateful for the sheriff's department for their intervention. And believe india can be another recovery success story, instead of a cautionary tale. For "Good morning America," Reena ninan, ABC news, New York.

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